Disclosed herein is a refrigerator. Light sensor signals from a plurality of light sensors are processed such that localised shielding of the ambient light at the location of one or more of the light sensors is identified. The invention is comprised of one Primary Steel Plate, plus a reusable hand-held tool for its installation. A second tow ball of a second dimension is fixedly mounted to a second of the side surfaces. The specific design of the amplifier stages enables the two pump power levels to be suitable for different fiber types so that the advantages of a multi-stage amplifier are maintained whilst simplifying the pump source requirements.